/// Copyright (c) 2020 Razeware LLC
///
/// Permission is hereby granted, free of charge, to any person obtaining a copy
/// of this software and associated documentation files (the "Software"), to deal
/// in the Software without restriction, including without limitation the rights
/// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
/// copies of the Software, and to permit persons to whom the Software is
/// furnished to do so, subject to the following conditions:
///
/// The above copyright notice and this permission notice shall be included in
/// all copies or substantial portions of the Software.
///
/// Notwithstanding the foregoing, you may not use, copy, modify, merge, publish,
/// distribute, sublicense, create a derivative work, and/or sell copies of the
/// Software in any work that is designed, intended, or marketed for pedagogical or
/// instructional purposes related to programming, coding, application development,
/// or information technology.  Permission for such use, copying, modification,
/// merger, publication, distribution, sublicensing, creation of derivative works,
/// or sale is expressly withheld.
///
/// This project and source code may use libraries or frameworks that are
/// released under various Open-Source licenses. Use of those libraries and
/// frameworks are governed by their own individual licenses.
///
/// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
/// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
/// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
/// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
/// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
/// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
/// THE SOFTWARE.

import Foundation
import Alamofire

// Type: response category, i.e. A (article), D (disambiguation), C (category), N (name), E (exclusive), or nothing.
enum ResultType: String, Codable {
  case article = "A"
  case disambiguation = "D"
  case category = "C"
  case name = "N"
  case exclusive = "E"
}

struct Definition: Codable {
  let title: String
  let description: String
  let resultType: ResultType
  let imageURL: URL?
  
  enum CodingKeys: String, CodingKey {
    case title = "Heading"
    case description = "AbstractText"
    case resultType = "Type"
    case imageURL = "Image"
  }
}

final class DuckDuckGo {
  func performSearch(for term: String, completion: @escaping (Definition?) -> Void) {
    // 1
    let parameters: Parameters = [
      "q": term,
      "format": "json",
      "pretty": 1,
      "no_html": 1,
      "skip_disambig": 1
    ]
    
    // 2
    Alamofire.request(
      "https://api.duckduckgo.com",
      method: .get,
      parameters: parameters)
      .responseData { response in
        // 3
        guard
          response.result.isSuccess,
          let jsonData = response.result.value
          else {
            completion(nil)
            return
        }
        
        // 5
        let decoder = JSONDecoder()
        
        guard
          let definition = try? decoder.decode(Definition.self, from: jsonData),
          definition.resultType == .article
          else {
            completion(nil)
            return
        }
        
        completion(definition)
    }
  }
}
